diff --git a/src/bro.bif b/src/bro.bif
index 6a79a1ac9d..0b880de379 100644
--- a/src/bro.bif
+++ b/src/bro.bif
@@ -466,17 +466,18 @@ function system%(str: string%): int
 ##
 ## str: The command to execute.
 ##
-## env: A :bro:type:`set` or :bro:type:`table` with the environment variables
-##      in the form of key-value pairs (where the value is optional).
+## env: A :bro:type:`table` with the environment variables in the form
+##      of key-value pairs. Each specified environment variable name
+##      will be automatically prepended with ``BRO_ARG_``.
 ##
 ## Returns: The return value from the OS ``system`` function.
 ##
 ## .. bro:see:: system str_shell_escape piped_exec
-function system_env%(str: string, env: any%): int
+function system_env%(str: string, env: table_string_of_string%): int
 	%{
 	if ( env->Type()->Tag() != TYPE_TABLE )
 		{
-		builtin_error("system_env() requires a table/set argument");
+		builtin_error("system_env() requires a table argument");
 		return new Val(-1, TYPE_INT);
 		}
 
diff --git a/testing/btest/Baseline/bifs.system_env/testfile b/testing/btest/Baseline/bifs.system_env/testfile
index 8b13789179..31e0fce560 100644
--- a/testing/btest/Baseline/bifs.system_env/testfile
+++ b/testing/btest/Baseline/bifs.system_env/testfile
@@ -1 +1 @@
-
+helloworld
diff --git a/testing/btest/bifs/system_env.bro b/testing/btest/bifs/system_env.bro
index 26e40b883f..23928e9b10 100644
--- a/testing/btest/bifs/system_env.bro
+++ b/testing/btest/bifs/system_env.bro
@@ -7,17 +7,17 @@ event bro_init()
 	local vars: table[string] of string = { ["TESTBRO"] = "helloworld" };
 
 	# make sure the env. variable is not set
-	local myvar = getenv("TESTBRO");
+	local myvar = getenv("BRO_ARG_TESTBRO");
 	if ( |myvar| != 0 )
 		exit(1);
 
 	# check if command runs with the env. variable defined
-	local a = system_env("echo $TESTBRO > testfile", vars);
+	local a = system_env("echo $BRO_ARG_TESTBRO > testfile", vars);
 	if ( a != 0 )
 		exit(1);
 
 	# make sure the env. variable is still not set
-	myvar = getenv("TESTBRO");
+	myvar = getenv("BRO_ARG_TESTBRO");
 	if ( |myvar| != 0 )
 		exit(1);
 	}